Utilizing ultrasonification to disrupt biological structures has long been recognized in the medical and scientific research field as well as the industrial field. As early as the 1920's, ultrasonification has been known to cause a killing effect upon organisms as reported in various scientific journals.
In American Laboratory, "Ultrasonic Disruption", October 1975 pp. 75-85, Howard Alliger reported fragile cells, such as blood cells and Esherichia Coli are disrupted when exposed to ultrasonification. The sonificated bacteria was reported by Alliger to have thinner cell walls than non-sonificated bacteria. This thinning of the cell walls was attributed to the freeing of cytoplasmic layers from the cell wall.
In a later article published in the Journal of Dairy Research, "Effect of Combined Ultrasonic and Heat Treatment, (thermoultrasonification) on the survival of Staphylococcus aureus", 1987, pp 61-67, Juan Ordonez and others reported ultrasonification in conjunction with heat was an effective treatment for destruction of Staphylococcus aureus and was more effective than heat alone. The authors further noted treating solutions with ultrasonic waves had several other positive side effects such as: homogenizing of fat in milk; expelling of gases in solution; and increasing of antioxidant activity in milk.
In the book Ultrasound Its Chemical, Physical, and Biological Effect published in 1988 by VCH Publishers, R. E. Verrall and C. M. Sehgal summarized results obtained in studies performed to determine the origin of sonoluminescence (SL), which is the emission of light when ultrasound is applied to a medium containing dissolved gases. They reported sonoluminescence increased 10-20 times in a solution as pressure was applied. The studies reported by Verrall and Sehgal did not determine whether the increase in sonoluminescence was a result of an increase in cavitational intensity of individual events or the result of increase in the actual number of bursting bubbles. However, the experiments unequivocally showed that pressure increased the cavitation effect in the saturated solution.
Specifically, the studies reported by Verrall and Sehgal substantiate the linear dependence of ultrasonic power to hydrostatic pressure. The reported studies showed that the ultrasonic power applied will determine the maximum pressure that can be applied to the solution, liquid or slurry. In conclusion, the intensity of the ultrasonic power i.e. sound field will determine the numerical value of pressure that is necessary to obtain the maximum cavitational intensity for the particular ultrasonic power. Therefore, in my invention when the liquid or slurry is being sonificated with a ultrasonic power source of a specific frequency and intensity, the numerical value of pressure necessary for maximum cavitational effect will be constant for that particular ultrasonic power source.
Studies by the inventor performed at Kenneth E. Johnson Research Center Consortium for the Space Life Sciences Microbiology Laboratory, Huntsville, Alabama yielded results that a lower temperature could be used to obtain a particular percentage kill of microbes when ultrasonification was utilized with heat. The maximum temperature necessary to obtain "sterility" was 44 C.(111 F.). The present temperatures used in the food industry today to obtain sterility are much higher. Two medias, which represented characteristics of various beverages found in the food industry, were used in the Life Sciences test--a very hypotonic nutrient broth, similar to milk, and purified water; and different microbes with different cell wall structures were used--Esherichia Coli, Staphylococcus aureus and Bacillus stearothemophilis. The above microbes represented the various cell wall structures of microbe types which contribute to food industry contamination and spoilage. The Life Sciences study teaches that the degree and duration of heat necessary to obtain sterility is lowered when ultrasound is used in conjunction with heat.
My invention by using pressure in conjunction with the heat and ultrasonification will be able to further lower the duration and intensity of heat necessary to obtain sterilization by increasing the effectiveness of the ultrasonification and heat treatment. As the Life Science study implies when ultrasonification is applied along with heat the intensity of heat necessary to obtain sterility decreases; therefore, it can be conclude that as the ultrasonification i.e. cavitional effect is increases such as when pressure is applied the heat (temperature) necessary to achieve an acceptable percentage killed will be lowered and, also, the exposure time to a particular temperature will be lowered. My invention will result in flash sterilization being able to be carried out at a lower temperature and for a shorter period of time.
My invention combines heat, ultrasonification and pressure to obtain an effective and efficient bactericide for beverages and food products in the food industry. My invention particular increases the effectiveness of heat and ultrasonification sterilization by utilizing pressure and saturation of the liquid or slurry by gas or gaseous molecules to increase the cavitational effect of ultrasonification; therefore, lowering the duration and intensity of heat necessary to obtain sterilization of a liquid or slurry.